I posted this once before. Message here is the 21ft rule doesn't give anyone a license to shoot. Other factors are involved.
http://www.policeone.com/writers/col...rticles/102828
For more than 20 years now, a concept called the 21-Foot Rule has been a core component in training officers to defend themselves against edged weapons.
Originating from research by Salt Lake City trainer Dennis Tueller and popularized by the Street Survival Seminar and the seminal instructional video "Surviving Edged Weapons," the "rule" states that in the time it takes the average officer to recognize a threat, draw his sidearm and fire 2 rounds at center mass, an average subject charging at the officer with a knife or other cutting or stabbing weapon can cover a distance of 21 feet.
The implication, therefore, is that when dealing with an edged-weapon wielder at anything less than 21 feet an officer had better have his gun out and ready to shoot before the offender starts rushing him or else he risks being set upon and injured or killed before he can draw his sidearm and effectively defeat the attack.
"Unfortunately, some officers and apparently some trainers as well have 'streamlined' the 21-Foot Rule in a way that gravely distorts its meaning and exposes them to highly undesirable legal consequences," Lewinski says. Namely, they have come to believe that the Rule means that a subject brandishing an edged weapon when positioned at any distance less than 21 feet from an officer can justifiably be shot.
For example, an article on the 21-Foot Rule in a highly respected LE magazine states in its opening sentence that "a suspect armed with an edged weapon and within twenty-one feet of a police officer presents a deadly threat." The "common knowledge" that "deadly force against him is justified" has long been "accepted in police and court circles," the article continues.
Statements like that, Lewinski says, "have led officers to believe that no matter what position they're in, even with their gun on target and their finger on the trigger, they are in extreme danger at 21 feet. They believe they don't have a chance of surviving unless they preempt the suspect by shooting.
"However widespread that contaminated interpretation may be, it is
NOT accurate. A suspect with a knife within 21 feet of an officer is
POTENTIALLY a deadly threat. He does warrant getting your gun out and ready. But he cannot be considered an actual threat justifying deadly force until he takes the first overt action in furtherance of intention--like starting to rush or lunge toward the officer with intent to do harm. Even then there may be factors besides distance that influence a force decision.
continued at link...